The invention relates to a test printing apparatus and a method for test printing, in which printing ink is printed on a test strip.
U.S. Pat. No. 5,415,054 describes such a test printing apparatus. This apparatus can be used to simulate process parameters occurring on a rotary press, in order to determine suitable parameters for processing the combination of types of substrate and printing ink. Relevant parameters may be, for example: the pressure applied by the printing surface to the substrate, and the speed with which the printing surface rolls over the substrate. The drive of the bearing surface is therefore controllable for controlling the speed of movement of the bearing surface along the rotary path, and the pressure the printing surface applies to the test substrate on the bearing surface is also controllable in this appliance. The rotatable bearing surface in this apparatus is designed as a segment of the outer surface of a main disc and the printing surface is formed by a rubber outer surface of a printing disc which outer surface can be pressed against the outer surface of the main disc. Several of such printing discs can be provided which can be pressed against the main disc independently of each other.
When test printing is performed with printing ink that cures and/or dries under the influence of ultraviolet radiation, the substrate is removed from the bearing surface and transferred to an ultraviolet irradiator. This is laborious and variations in ambient conditions and the time that elapses between the printing and irradiation of the printed substrate can affect the result of the printing tests.
U.S. Pat. No. 4,592,276 describes an apparatus in which articles, such as bottles, are rotated in a printing station, are subsequently conveyed on a carrier to a curing station, and once again rotated in the curing station. This apparatus is complex and intended for printing circumferential surfaces of articles with an at least partly cylindrical form. However, this apparatus is rather complex due to the need to rotate the articles in two places and to convey them from the printing station to the curing station.
It is an object of the invention to provide a simple solution that enables a test substrate printed for testing purposes to be cured and/or dried by the impact of ultraviolet radiation without it being necessary to manually transfer the test substrate from a test print appliance to a curing appliance.
This object is achieved according to a first aspect of the invention by providing a test printing apparatus for test printing, in which printing ink is printed on a test substrate.
This apparatus is equipped with:
a bearing surface for bearing the test substrate, circulatable along a rotary path,
a drive for circulating the bearing surface;
a detector for detecting at least defined rotary positions in a sense of rotation of the bearing surface;
at least one printing surface adjacent the path of the bearing surface for causing the printing surface to roll over a test substrate on the bearing surface for printing the test substrate;
a control communicating with the detector and with the drive for controlling the drive, depending on the position of the bearing surface, for causing the bearing surface to move in different sections of the rotary path with predetermined, different speeds in the sense of rotation; and
an ultraviolet irradiation assembly mounted adjacent the path of the bearing surface for emitting ultraviolet radiation against the test substrate attached to the bearing surface.
Here, the control is arranged for actuating the drive for imparting to the bearing surface a speed in the sense of rotation which, during the irradiation, is different from the speed which the drive imparts to the bearing surface during the printing of the test substrate.
The invention can also be embodied in an irradiation assembly for coupling to a test printing apparatus for test printing, equipped with:
an ultraviolet radiation source and a light channel with an exit aperture for guiding ultraviolet radiation to an irradiatable part of a rotary path of a bearing surface for bearing a test substrate;
a control input for connection to a control unit of the test printing apparatus for receiving control signals from the control unit; and
a light emission operating device for operating the emission of UV radiation in response to control signals received through the control input.
With this, a test printing apparatus can be extended to form a test printing apparatus according to the invention.
According to another aspect of the invention, this object is achieved by using a method for test printing, in which printing ink is printed on a test substrate, including:
circulating along a rotary path a test substrate borne by a bearing surface circulatable along the path;
detecting at least defined positions in the sense of rotation of the bearing surface;
rolling a printing surface over a test substrate on the bearing surface in a position along the rotary path which the test substrate passes along for printing the test substrate;
controlling the drive, depending on the position of the bearing surface, for causing the bearing surface to move in different sections of the rotary path with predetermined, different speeds in a sense of rotation; and
after printing, emitting ultraviolet radiation against the test substrate in an irradiation section of the rotary path;
wherein the bearing surface, during the emission of ultraviolet radiation against the test substrate, is moved with a different speed in the sense of rotation than during the printing of the test substrate.
As the drive of the circulating surface is controlled for causing the bearing surface bearing the test substrate to move with different speeds in the sense of rotation during the printing and the curing of the ink by irradiation with ultraviolet radiation, the detector for determining at least defined positions of the bearing surface and the controllable drive are not only utilized for causing the printing surfaces to roll over the test strip during printing with controlled, optionally different speeds, but also for causing the test substrate to move with an adjusted speed during the curing. Thus, the speed of the test substrate is adjusted in a simple manner to the time needed to expose the test substrate to ultraviolet radiation for the desired length of time. In addition, the test substrate does not need to be taken off the bearing surface for curing and/or drying and the construction can be kept simple, because printing and irradiation take place along the same rotary path.